Effects of exhausting exercise on muscle cytokine IL-6 and oxidative stress in exercise-trained and untrained rats

A strenuous physical activity is known to lead to a low degree of inflammatory response and muscle damage in the organism.In this research, long term exercise-trained (chronic) and untrained (acute) rats were forced to make exhausting exercise. Muscle damage, muscle?s immune response (IL-6) against this damage and free oxygen radicals reported to be responsible for this damage were compared in both groups, sacrificed just after exhaustion, 1 day and 3 days following exhaustion. Extends of damage were assessed histologically; IL-6, immuno-histochemically; levels of oxidants (MDA); antioxidants (GSH, RSH) and nitric oxide spectrophotometrically in Histology and Physiology Laboratories of Gazi University Medical Faculty.After exhaustion, findings of damage, IL-6 immunoreactivity and oxidants were found higher and antioxidants were found lower in acutely running rats comparing to the chronically exercise-trained rats. In both groups, muscle damage was found to begin and IL-6 and oxidants were found to increase significantly compared to controls just after exhaustion; however maximum damage, IL-6 immunoreactivity and oxidant levels emerged in the groups that were analyzed 1 day after exhaustion. Three days after exhaustion, IL-6 and oxidant levels were found to decrease and especially in the chronically training group, it approached approximately to the level of controls. In the acutely running group, although IL-6 involvement decreased, plasma oxidant and nitric oxide levels still were found significantly higher and antioxidant levels lower compared to controls. It was concluded that regeneration process developed slower in them comparing to exercise-trained group.In conclusion, chronic exercise training, limiting the elevation of pro-inflammatory cytokines (IL-6) and free radicals, provided the exercise-related muscle damage at lower levels. The fact that findings of muscle damage related to muscle strain reached maximum 1 days after exhausting exercise, IL-6 and oxidant levels followed this course make us think that, those pro-inflammatory factors might be suppressed by another agent -most probably by cortisol - in the beginning of the muscle damage and exacerbated one day after exhaustion, probably after the end of the cortisol?s dominant effect.Key Words: Exhausting exercise, Myokines, Oxidants, Muscle damage